Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
  • H05K3/4038—Through-connections; Vertical interconnect access [VIA] connections
  • H05K3/4053—Through-connections; Vertical interconnect access [VIA] connections by thick-film techniques
  • H05K3/4069—Through-connections; Vertical interconnect access [VIA] connections by thick-film techniques for via connections in organic insulating substrates
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
  • H05K3/4038—Through-connections; Vertical interconnect access [VIA] connections
  • H05K3/4053—Through-connections; Vertical interconnect access [VIA] connections by thick-film techniques
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09818—Shape or layout details not covered by a single group of H05K2201/09009 - H05K2201/09809
  • H05K2201/09981—Metallised walls
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/01—Tools for processing; Objects used during processing
  • H05K2203/0195—Tool for a process not provided for in H05K3/00, e.g. tool for handling objects using suction, for deforming objects, for applying local pressure
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/14—Related to the order of processing steps
  • H05K2203/1453—Applying the circuit pattern before another process, e.g. before filling of vias with conductive paste, before making printed resistors
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
  • H05K3/12—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
  • H05K3/1216—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns by screen printing or stencil printing

Definitions

• PCB's known as "double-sided" PCB's, namely those consisting of a laminated board plated with copper on both sides and having the tracks of the circuit printed on both sides.
• This type of PCB generally raises the problem of making the electrical connection between the tracks printed on the two opposing sides of the laminated board.
• This problem is currently resolved by making numerous through holes on the opposing tracks between which the electric connection jumper is to be made; these holes - known technically as "through holes" - are then filled with conductive polymer lacquer such as copper or silver paste, whose purpose is to ensure the electric connection between the two tracks with the entry and exit of each hole.
• conductive polymer lacquer such as copper or silver paste
• the simplest and less expensive of the filling techniques used today consists of a silk screen printing operation during which a drop of conductive lacquer is placed in each hole; the first problem of this technique is that it involves two printing stages, one for each side of the circuit in order to ensure that a sufficient amount of lacquer is placed in each hole to fill it completely so as to guarantee the connection between the two mouths of each hole.
• the considerable quantity of lacquer that with this first filling technique tends to accumulate in each hole for the reason explained above, often creates problems during the subsequent welding stage during which the electronic components are fixed onto the PCB.
• the circuit is in fact subject to high temperatures which may cause a phenomenon known as "blowhole"; this is a phenomenon whereby the conductive lacquer in the hole cracks due to bursting of small drops of solvent which do not evaporate during the silk screen printing process because of the excessive accumulation of paste and thus remain trapped in the paste.
• the purpose of this invention is to design a new system for filling the "through holes " of double-sided PCB's without any of the above problems and which is simple and economical to realise and does not require the use of special and expensive plants and tooling.
• the system according to the invention is based on the idea of pushing and spreading in the hole a small amount of conductive lacquer using a suitable punch which not only pushes the lacquer deep into the hole but also spreads it on the inner side wall of the hole which is in this way coated by a layer of conductive lacquer having a thickness equal to the distance between the external wall of the punch and the internal wall of the hole.
• the filling system involves the following operating stages: - silk screen printing of one of the two sides of the PCB in order to deposit a small amount of conductive lacquer on all the "through holes”; - insertion into all the "through holes” of the same number of corresponding punches which push and spread in each hole the lacquer deposited on the mouth of each hole during the previous printing stage - extraction of the punches from the corresponding "through holes”.
• - figs. 1 - 4 are a schematic view of one of the "through holes" of the circuit as the PCB is subjected to the filling system according to the invention.
• fig. 1 shows a section (1) of a double-sided PCB cross-sectioned over one of its "through holes" (2) into which the conductive lacquer for the connection of the two opposing tracks (P) crossed by holes (2), has not yet been inserted.
• the filling system includes the following operating stages: a) silk screen printing of one (1 a) of the two sides of the PCB (1) in order to deposit a small amount of conductive lacquer (3) on the mouth of all the "through holes” (2), as shown in fig. 2; b) insertion into each "through hole” (2) of a corresponding punch (4) which pushes and spreads the conductive lacquer (3) deposited on the mouth of each hole (2), into the hole (2), as shown in fig. 3; c) extraction of the punches (4) from the corresponding "through holes” (2) as shown in fig. 4.
• the inner side wall (2a) of the holes (2) is completely coated by a layer of conductive lacquer (3) having a thickness equal to the difference between the outer wall of the punch (4) and the inner wall of the hole
• the first silk screen printing stage as described in point a), is performed with conventional operating modalities and times.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Printing Elements For Providing Electric Connections Between Printed Circuits (AREA)
• Dc Digital Transmission (AREA)
• Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=11357175

Family Applications (1)

Country Status (3)

Citations (4)

• 1996
  • 1996-03-13 IT IT96MC000032A patent/IT1289327B1/it active IP Right Grant
• 1997
  • 1997-03-06 WO PCT/IT1997/000049 patent/WO1997034451A1/en active Application Filing
  • 1997-03-06 AU AU19388/97A patent/AU1938897A/en not_active Abandoned

Patent Citations (4)

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